Technical Abstract:
Grain hardness is an important quality trait in sorghum. Grain hardness has been linked to milling and food quality as well as resistance to insects and mold. Despite the importance of grain hardness in sorghum, its biochemical basis is still not well understood. In sorghum, the grain is composed of areas of both hard and soft endosperm. Past research has demonstrated that the storage protein composition of these endosperm types differs, and hypotheses on protein cross-linking have been made to explain grain hardness. Our research into the polymeric protein composition and kafirin subclass composition in sorghum has confirmed that kafirin composition does vary between hard and soft endosperm, with soft endosperm having higher relative amounts of gamma kafirin compared to hard endosperm. Furthermore, the crosslinking of the kafirins appears to differ as the molecular weight distribution of polymeric proteins differs between hard and soft endosperm. The distribution of disulfide bonds and free sulfhydryl bonds also differed between hard and soft endosperm.